You have to do the math for yourself. What kind of meals would you eat? How many would be Table Service? Do you drink alcohol? etc. etc.
Then which dining plan would you choose?
Here is what I did last time - I looked at our trip, and figured out what meals we would normally get for that trip. Then what meals we would typically get, and added it all up (fairly recent menus with prices are available online).
Then I figured out what portion of those were covered by the TIW card that weren't already covered by the AP and/or DVC, and figured out the costs for those specifically. If that came out to more than $375 before discount, then I would come out ahead with the TIW card.
Then I looked at the standard
DDP (1TS, 1QS, 1 Snack). I figured out what adjustments I would have to make to use it, and the cost. If that came out to be less than what I figured out before, the DDP would make sense.
Then I compared the two - applied the 20% discount to the eligible meals with TIW, and compared the total for everything against the DDP cost, and figured out which is better.
In our case, the DDP didn't make any sense as the planned meals worked out less, especially since we didn't have as many TS meals planned anyways. Sure we could have added the TS meals, but that meant spending more money to save a little.
Plus, if you can get another trip out of the TIW card before it expires, its even better.